Leaf orientation of soybean seedlings: II. Receptor sites and light stimuli.

(...)The pulvinus was the receptor site for light that stimulates both diaheliotropic and paraheliotropic leaf movement. (...)Blue light was necessary for both diaheliotropism and paraheliotropism.(...)There was one peak between 410 and 440 nm and one between 470 and 490 nm. A nonphytochrome photoreceptor located in the pulvinus used blue light, in conjunction with other factors, to determine leaf orientation and thereby regulate light interception of leaves of soybean seedlings